Normal sudoku rules apply. The circles contain a complete set of the digits from 1 to 9. In other words, no two circles may contain identical digits. Pea Lines: The sum of the digits on a line strictly between two circles is equal to a concatenation of the two values in the circles, in some order. For instance, 3_346_1 could be a valid split pea line, as 3+4+6=13, which is 1 concatenated with 3.